The inspection of large plants for power generation, such as gas or steam turbines, is of great interest in order to detect damage in time and to minimize the downtime of such plants.
Particularly large cast parts of these plants, such as steam chests, i.e. the structures which connect the live steam feed lines to the steam turbine and contain all the necessary valves (see, for example, EP-A1-0 005 616 or U.S. Pat. No. 4,592,699) frequently display crack formation because they are exposed to high pressures and temperatures. If such a crack formation is detected in time, that is to say at an early stage, suitable measures can be initiated and therefore serious consequences avoided.
Whereas an inspection on the outer side of such structures is comparatively simple, the inspection of the inner walls becomes more difficult due to the fact that the access openings to the inner spaces, in comparison to the inner spaces themselves, are often very narrow and that the inner walls have irregular, especially concave, shapes which restrict the space for an inspection device which is introduced into the inner space.